Growth stimulants are still controversial about toxicity

Plant hormones or growth stimulants have been synthesized since 1931. For more than 70 years since their inception, they have been widely used by farmers. However, there is still much controversy about the toxicity of plant hormones.

Researchers in plant biology believe that these hormones use all of their influence through a specific receptor in the target cells, similar to the mechanism found. in animals. 5 long-identified plant hormones: auxin, cytokinin, gibberellin, abscisic acid, and ethylene. Currently, scientists continue to explore other plant hormones.

70 years of birth of growth stimulants

Auxin, the first plant hormone discovered by scientists. It is primarily responsible for protein synthesis and regulates many growth and development processes of plants. These processes include: skyrocketing, growth roots, ripe fruits, flowering .

In the book 'The Movement Power of Plants - The Power of Movement in Plants' published in 1880, Charles Darwin described for the first time the effects of light on the leaf movement of canary grasses ( Phalaris canariensis).

Sprouts are a special type of leaf that comes from the first nodule covering the outer shell of the germinal germ during the germination stage of the seed, to protect young plants until it reaches the ground. When light hits the sprouts, it bends in the direction of the light. If its tops are covered by an aluminum layer, no bending motion occurs.

Auxins, growth plant hormones, help stimulate cell growth.(Photo: images.the-scientist.com)

Darwin's experiments suggest a suggestion that the tip of the sprouts has a plant tissue that is responsible for receiving light and producing signals that propagate down into the lower body where physiological reactions take place. makes bending happen. After that, Darwin removed the tips of the cotyledons, and displayed the rest to light. The bend did not occur, further confirming the results of the previous test.

In 1885, a scientist named Salkowski discovered indole-3-acetic acid (IAA) in fermentation media. But the process of extracting similar products in plant tissues failed for nearly 50 years.

In 1926, a Dutch graduate student named Fritz Went published a report describing a method of isolating growth stimulants by placing white agar blocks below the top of the sprouts for a period of time. Certainly then take out and place them on other stems that have been tops.

After placing the blocks, the stems began to grow again. In 1928, Went developed a method of quantifying this plant growth stimulant. His results suggest that a proposal of the bending activities of the trunk will correspond to the amount of growth in the jelly.

Went's works have created a great influence on later studies of plant growth stimulants.

Went is often known as the pioneer using the term 'auxin', but actually has to mention Kogl and Haagen-Smit. They were the ones who purified the auxentriolic acid mixture (auxin A) from human urine in 1931. After that, Kogl isolated other compounds from urine with the same structure and function as auxin A. , including IAA.

The most common auxin, indoleacetic acid (IAA), is usually formed near the peak of growth and then goes down. That process makes the young leaves grow longer. IAA stimulates plants to grow towards light and develop roots.

In 1954, a council of plant physiologists was established to identify auxin groups. This term comes from Greek, meaning 'growth'. Compounds are collectively called auxins if they are synthesized in plants and are substances that share similar activities with the IAA.

Many controversies about toxicity

Today, hormones are widely used for commercial purposes. For example, growth hormone helps to increase lean meat for both cattle and pigs to have animals that gain weight without fat.

Bovine somatotropin (BST), which helps to produce high-yielding dairy cows. Hormones are often used by farmers to increase the success rate in artificial insemination .

The United States Food and Drug Administration (FDA) has agreed to use BST in November 1993. However, the safety and morality of using the collection is still controversial. Concerns about the side effects of the BST so that Canada and many European Community countries issued a ban on its use.

For plants, many auxin groups are used to promote ripe fruit without pollination, or to make cuttings root. And more like synthetic auxins will become effective herbicides.

Herbicides belonging to this group are widely used around the world than any other. The 2,4-D herbicide has provided a stimulus for agricultural chemistry.

According to the National Environmental Protection Agency (EPA) information on the national telecommunications network of National Pesticide Telecommunications NetWork, each type of synthetic auxin carries different toxicity. For example, 2,4-D may be toxic to rats depending on the formulation formula (acid, amine, or ester). In general, this is a substance that is less harmful to animals.

Some recent studies show that the daily diet of rats and dogs has a sufficient amount of 2,4-D, which in the long term exhibits weight loss and chemical composition changes. in blood.

For people, EPA ranks 2,4-D in group D (ie not the risk group for human cancer). According to EPA research on regular farmers exposed to 2,4-D, there is little evidence that it is a carcinogen.

However, excessive use of 2,4-D can affect the nervous system and digestion. Some manifestations of 2,4-D infection include: muscle weakness, reflex loss, vomiting, sweating, headache, dizziness, and immediate hypotension . 2,4-D Can be excreted from the body. For mice, within 53 hours, about 50% of 2,4-D doses were excreted. For sheep, a dose of 2,4-D can be completely eliminated within 96 hours.

The structure is acid or amine, 2,4-D can be excreted from the body quickly without causing depletion. As for ester, 2,4-D must be converted into acid before being excreted.

Huong Cat (Source: MSN, The Advanced Light Source, EPA, VNN)